Publications de Martin Vetterli

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The digital Fourier transform (DFT) and the adaptive least mean square (LMS) algorithm have existed for some time. This paper establishes a connection between them. The result is the "LMS spectrum analyzer," a new means for the calculation of the DFT. The method uses a set ofNperiodic complex phasors whose frequencies are equally spaced from dc to the sampling frequency. The phasors are weighted and then are summed to generate a reconstructed signal. Weights are adapted to realize a best least squares fit b

Digital signal processing with filter banks, that is filtering a single signal with several filters and subsequent subsampling (or the converse, that is multiplexing), is an important subject with numerous applications (sub-band coding, transmultiplexing). This work first develops an analysis framework for signal processing by means of filter banks. The framework is based on matrix notation and a generalized polyphase representation of filter banks. This powerful formalism is used to derive fundamental resu

A field measurement campaign was conducted from June to October 2009 in a 20 km2 catchment of the Swiss Alps with a wireless network of 12 weather stations and river discharge monitoring. The objective was to investigate the spatial variability of meteorol ...

With society’s increasing reliance on digital data sharing, the protection of sensitive information has become critical. Encryption serves as one of the privacy-preserving methods; however, its realization in the audio domain predominantly relies on signal processing or software methods embedded into hardware. In this paper, we introduce LenslessMic, a hybrid optical hardware-based encryption method that utilizes a lensless camera as a physical layer of security applicable to multiple types of audio. We sho

In this paper, we introduce a novel technique for adaptive scalar quantization. Adaptivity is useful in applica- tions, including image compression, where the statistics of the source are either not known a priori or will change over time. Our algorithm uses previously quantized samples to estimate the distribution of the source, and does not require that side information be sent in order to adapt to changing source statistics. Our quantization scheme is thus backward adaptive. We propose that an adaptive q

We propose a new method for imaging sound speed in breast tissue from measurements obtained by ultrasound tomography (UST) scan- ners. Given the measurements, our algorithm finds a sparse image representation in an overcomplete dictionary that is adapted t ...

The spatialization of the sound field in a room is studied, in particular the evolution of room impulse responses as a function of their spatial positions. It was observed that the multidimensional spectrum of the solution of the wave equation has an almost bandlimited character. Therefore, sampling and interpolation can easily be applied using signals on an array. The decay of the spectrum is studied on both temporal and spatial frequency axes. The influence of the decay on the performance of the interpola

In this study, the scalar roughness for sensible heat in the temperature profile (z0,h) is determined based on direct skin temperature measurements and profiles of wind and temperature in a complex urban environment. Typically, skin temperatures are inferred from remotely sensed data (e.g. satellite). However, in complex environments like cities, strong heterogeneities exist in the temperature fields at scales that cannot be resolved by remote sensing. Because they are more precise, in situ measurements, wh

Lensless imaging seeks to replace/remove the lens in a conventional imaging system. The earliest cameras were in fact lensless, relying on long exposure times to form images on the other end of a small aperture in a darkened room/container (camera obscura). The introduction of a lens allowed for more light throughput and therefore shorter exposure times, while retaining sharp focus. The incorporation of digital sensors readily enabled the use of computational imaging techniques to post-process and enhance r

The limitations of commonly used separable extensions of one-dimensional transforms, such as the Fourier and wavelet transforms, in capturing the geometry of image edges are well known. In this paper, we pursue a "true" two-dimensional transform that can c ...

We consider the problem of estimating sparse communication channels in the MIMO context. In small to medium bandwidth communications, as in the current standards for OFDM and CDMA communication systems (with bandwidth up to 20 MHz), such channels are indiv ...

The Karhunen–Loève transform (KLT) is a key ele- ment of many signal processing and communication tasks. Many recent applications involve distributed signal processing, where it is not generally possible to apply the KLT to the entire signal; rather, the K ...

A fundamental aspect of the “I” of conscious experience is that the self is experienced as a single coherent representation of the entire, spatially situated body. The purpose of the present study was to investigate agency for the entire body. We provided ...

The standard separable 2-D wavelet transform (WT) has recently achieved a great success in image processing because it provides a sparse representation of smooth images. However, it fails to efficiently capture 1-D discontinuities, like edges or contours. ...

This paper presents the Simple Packet Combining (SPaC) error-correction scheme for wireless sensor networks. Nodes buffer corrupt packets, and when two or more corrupt versions of a packet have been received, a packet combining procedure attempts to recove ...

We address the problem of jointly localizing a robot in an unknown room and estimating the room geometry from echoes. Unlike earlier work using echoes, we assume a completely autonomous setup with (near) collocated microphone and the acoustic source. We first introduce a simple, easy to analyze estimator, and prove that the sequence of room and trajectory estimates converges to the true values. Next, we approach the problem from a Bayesian point of view, and propose a more general solution which does not re

We consider the rate-distortion problem for sensing the continuous space-time physical temperature in a circular ring on which a heat source is applied over space and time, and which is allowed to cool by radiation or convection. The heat source is modelled as a continuous space-time stochastic process which is bandlimited over space and time. The temperature field is the result of a certain continuous space-time convolution of the heat source with the Green's function corresponding to the heat equation, wh

NOVELTY - At least some of wireless terminals can communicate over wireless links (2) in one or several hops with at least some of the other wireless terminals. The distances (dij) to one-hop neighbors may be measured in a number of the wireless terminals (1), using the distances measured in at least two terminals (1) to compute the location (x,y) of at least one other wireless terminal. USE - For determining the relative position of wireless terminals in a network without using GPS. ADVANTAGE - Generates a

Video coding has been investigated for the novel application of video transmission over packed-switched networks. The underlying design goals are presented, together with a software implementation of a coding scheme, which divides the input signal into frequency bands in all three dimensions, seems promising in that it lends itself to parrallel implementation, is robust enough to handle errors due to lost packets, and yields high compression with sustained good quality. Moreover, it may be well integrated w

Martin Vetterli

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Fundamental relations between the LMS algorithm and the DFT

Analyse, synthèse et complexité de calcul de bancs de filtres numériques

Hydrologic response of an alpine watershed: Application of a meteorological wireless sensor network to understand streamflow generation

LenslessMic: Audio Encryption and Authentication via Lensless Computational Imaging

Adaptive scalar quantization without side information

Ultrasound Tomography with Learned Dictionaries

The Plenacoustic Function and its Sampling

Determination of the Thermal Roughness Length for a Built Environment

LenslessPiCam: A Hardware and Software Platform for Lensless Computational Imaging with a Raspberry Pi

The Contourlet Transform: An Efficient Directional Multiresolution Image Representation

Estimation of Sparse MIMO Channels with Common Support

The Distributed Karhunen-Loève Transform

Feeling in control of your footsteps: Conscious gait monitoring and the auditory consequences of footsteps

Space-frequency quantization for image compression with directionlets

Packet Combining in Sensor Networks

EchoSLAM: Simultaneous Localization and Mapping with Acoustic Echoes

Rate-Distortion Problem for Physics Based Distributed Sensing

System and method for generating and maintaining a relative positioning system without GPS

Rate-Distortion Problem for Physics Based Distributed Sensing

Subband coding of video for packet networks